PHYS 1111 1nd EditionExam # 2 Study Guide Lectures: 7 - 15Chapter 5:- Force: A push or pull; has a magnitude and direction so is a vector- Newton’s first law of motion: o Inertia: An object at rest remains at rest as long as no net force acts on ito An object moving with a constant velocity continues with the same direction and speed as long as no net force acts on it- Newton’s second law of motion: ∑F=m ao If no net force, acceleration is zero so velocity is constant - Newton’s third law of motion: for every force that acts on an object, there’s a reaction fore acting on a different object that’s equal in magnitude and opposite in direction- If an elevator is at rest, N=mgo a>0, n>mg (Feel heavier)o a<0, N<mg (Feel lighter)o a=-g, N=0 (Weightlessness)Chapter 3 (section 6):- If the reference frame is at rest or moving at a constant velocity, there is a inertial reference frame- If the reference from is acceleration, then it is a non-inertial from of reference (the first and second laws of Newton fail!)- There is never a 0 velocity in the universe because there is no centerChapter 6:- Kinetic friction: the friction encountered when surfaces slide against one another with finite relative speed (ex. Car skidding)ofK=μkN; a greater coefficient of friction= more friction against object- Static friction: keeps 2 surfaces from moving relative to one another (Ex. Car rolling)ofS=μSN ;As a force is applied, static friction increases until it’s max. Once max of static friction obtained, object begins to move and kinetic friction increases o Need more force to get object started than to keep moving- Hooke’s Law: Fx=−kx- Centripetal acceleration: he net force required to keep an object moving in a circular path; acp=v2r Chapter 12 (sections 1 and 2):- , G=6.67 × 10−11N m2/kg2- Object heavier on Earth than on the moon- Weight: force exerted by Earth’s gravity on an object - Kepler’s Laws of orbital motion:1. Plants follow elliptical orbits with sun at 1 focus of the ellipse2. Radius vector from the sun to the planets sweeps out equal areas in equal time3. Orbital period of a planet is proportional to the radius to the 3/2 powerChapter 7:-W=Fdcosθ; Units of work is Joules -−90<θ>90means work is positive and speed increases- 90<θ>270means work is negative and speed decreases- W= mgh-W=12mv2−12mv2-P=Fdt=Fv (measured on Watts)Chapter 8:- Potential energy: energy stored that can be converted to another kind of energy. o PE=mgh - Conservation of mechanical energy: E=KE +PE- Conservative force: a force in which work it does on an object doesn’t depend on the path (ex. gravity)- Nonconservative force: force for which work done depends on the path- If both forces exist, total work= conservative work + nonconservative work- Total energy of a universe is always constant. Energy is neither created nor destroyed—only converted - + Nonconservative work= increase in total mechanical energy- - Nonconservative work= decrease in total mechanical energyPractice problems:1. If a car travels around a curve which has a radius of 316 m and static friction of 0.78, what’s the maximum velocity the car can travel without skidding? ∑F=ma=N −mg=0 fS=ma=mv2r Car wont skid of the static friction is less than the maximum static frictional force so,mv2r<μSmgv =√μSgr=√0.78∗9.81∗316=49.12. A hockey puck slides across the ice. Initial velocity is 45 m/s and final velocity is 44.67 m/s. It slides 16 m. What is the coefficient of kinetic friction?∑F=−f =ma=μkmgW=μkmgdW=12mv2−12mv2=12m(44.672−452)μkm∗9.81∗16=12m(44.672−452)μk=0.0943. The velocity of the conveyer belt is 2 ft/s and the velocity of Ana with the conveyer is 1 ft/s. Whats the velocity of Anna as seen by Bob? Vab=Vac+Vcb=1fts+2fts=¿4. A particle starting from A is projected down a curved path. Upon leaving runway at point B, the particle is traveling straight upward and reaches a height of 4 m above the floor before falling back down. What’s the velocity at A?12m v2=mgh12v2=(9.81) (4−3)V= 4.43